The present invention concerns methods and systems for treatment of restenosis in body lumens such as blood vessels and, in particular, the treatment of in-stent restenosis.
Endoluminal stents are commonly used to treat obstructed or weakened body lumens, such as blood vessels and other vascular lumens. Numerous stents exist for this purpose, including those made of metals, fibers and other biocompatible materials. In general, the stent is either formed outside the body and then guided into place (e.g., adjacent to an obstruction) through a body lumen, or is positioned into place prior to formation and is then expanded and/or formed in situ within the body lumen. Once deployed, the stent can remain in the body lumen where it will maintain the patency of the lumen and/or support the walls of the lumen which surround it.
One factor impeding the success of stent technology in endoluminal treatments is the frequent occurrence of in-stent restenosis, characterized by proliferation and migration of smooth muscle cells within and/or adjacent to the implanted stent, causing reclosure or blockage of the body lumen. While the reasons for such smooth muscle cell proliferation following stent implantation are not entirely clear, it is believed that positioning of the stent within the body lumen may somehow irritate or damage the surrounding lumen walls and activate medial smooth muscle cells lining the walls.
Current methods for treating endoluminal restenosis, such as that which occur within or around a stent, generally consist of invasive procedures which physically remove atherosclerotic plaque by, for example, shaving or ablating the plaque, or by implanting a second stent. However, these procedures can cause further damage to the area of treatment and/or initiate further smooth muscle cell proliferation.
Accordingly, it is an object of the present invention to provide a substantially non-invasive method of treating in-stent restenosis by applying radiation to the smooth muscle cells which have grown within or around a stent implant in a manner that does not substantially damage the surrounding lumen wall or the stent itself, while resulting in a reduction of smooth muscle cell mass.